Body Switch
by illusione de ciel
Summary: Tsuna was in the middle of a shadow clone practice when he was suddenly zapped by lightning and got transported into another dimension. This is a story where Tsuna was once a ninja and Reborn was surprised his new student seemed a little eager in becoming the Mafia boss.
1. Chapter 1

**Note:** Genius!Tsuna, Calm!Tsuna, Quiet!Tsuna, Mature!Tsuna

 **Summary:** Tsuna was in the middle of a shadow clone practice when he was suddenly zapped by lightning and got transported into another dimension. This is a story where Tsuna was once a ninja and Reborn was surprised his new student seemed a little eager in becoming the Mafia boss.

 **Title:** Body Switch

It was one sunny Monday morning when a loud _BOOM_ went off at the Sawada house. Well, it was _supposed_ to be loud, except it also wasn't. It echoed within the lad's room; but beyond that, there were none.

A young "Sawada Tsunayoshi" stood in the middle of that room, hands suspended in some kind of form, the incantation in his head... simply stuck in his head. He broke from his stance and looked around. _Where the hell was he?_

.

To clarify things, I said "Sawada Tsunayoshi" because he was Sawada Tsunayoshi; but at the same time, not exactly him either. The lad transported in the room was an alternate version of a Sawada Tsunayoshi, heir to an old and powerful ninja clan — the Vongola — on a parallel world of Namimori. And because of that, he had considerably trained himself ever since he learned how to talk and walk at a very young age.

In fact, he was in the middle of said training — was finally perfecting his shadow clone technique — when he was suddenly zapped by lightning. Now, _lo_ , here he was, inside some kind of room he barely knew. Not to mention, _messy_. Tsuna hated messy.

"..."

If he was any other kid, he would've panicked by now. But he wasn't. He was Sawada Tsunayoshi, heir to an all-powerful ninja clan. "Strange" and "crazy" were the very definition of his life, and he was used to it. So he could take this one in stride as well.

First things first. He had to figure out who he was and where he was.

Since he wasn't transported using the bazooka of his friend, it was safe to say this body wasn't his future self. And to prove his point, his hands were still small, he barely reached the bed and the room was messy (he'd like to think his future self was more organised). He wanted to see his face. This problem would've been solved a lot faster if there was a mirror inside the room or...

Tsuna knitted his brows. A crazy idea just popped in his head. He breathed in deep, then redid the seal.

Ram.

Snake.

Tiger.

Immediately, a puff of smoke exploded in the room.

The moment it cleared, there were two more of him that appeared. In the relatively more normal days, what Tsuna would've noticed were his lack of skills and thus would've berated himself for still being so weak — for being able to release only two more clones (his definition of "perfecting" his shadow clone was releasing at least ten). Except, this time, the thing that surprised him was something else.

The clones that appeared were the exact copy of his past self.

Shadow clone should only clone his current self. Not past.

He was confused, and troubled.

This can only mean three things: his full body had transported with him, or that the clones did an additional layer of transformation and immediately projected his desired image (which was his old appearance), or... this body looked exactly like his past self.

The first two he was sure was already off the mark, because the moment he arrived in this world, Tsuna had felt _it_ — that brief "weirdness" or incompatibility as if he had just entered some vessel. Though he feels comfortable now, he was sure deep down this body was _not_ originally his. Not to mention, the clothes were also different. That said, if this was a completely different body, he reckon the skills shouldn't be up to par as well, ticking off that second option. _Ahhh..._ these things were making him anxious (he was still just a seven-year old kid after all)! He wished his mentor was here.

As if on cue, the door to his room opened.

Tsuna panicked for a while before sealing back all his clones. They instantly vanished in a puff of smoke, in time a woman with shoulder-length brunette hair came in from the half-opened door.

"Ara~ Tsu-kun, you're not yet dressed? Today is your first day of school! We must not be late."

"..."

"Tsu... kun?"

"...Ma... ma?"

It took a while before Tsuna could gather his bearings and croak out those syllables. He was visibly shocked. This woman looked exactly like his mother. And if the 'Tsu-kun' was any indication, he assumed he was _also_ called Tsuna in this world.

"Hmm?"

Nana was confused by the strange behaviour of her son. She actually expected Tsuna would still be asleep right now. If not, she thought he'd be complaining about school and act spoiled. Never did she expect her son to be fully awake and in complete surprise, then confusion while looking at her. _Well..._ maybe he's just shocked and confused because he had forgotten today was his first day of school? Now that seemed possible.

Nana sighed, before pushing said son to his bathroom. "Get dressed quickly, then go downstairs to eat breakfast." Tsuna followed without protest, earning a smile from his mother. The moment the bathroom door closed, Nana resisted the urge to scratch her head.

"..."

Her son was indeed strange this morning. No protests. No complaints. Maybe Tsuna finally matured and understood her difficulties? If that was the case, then it was good. So Nana simply smiled and let the matter drop, before naively and happily going back to her cooking. She was the kind to never trouble herself on small matters like these anyway.

=.=.=

Tsuna barely arrived on time.

Nana thought she'd stay for a while to help her son adjust around school; however, seeing him maturely and confidently take a random seat without much of a fuss, she smiled at Tsuna not too soon before excusing herself. She was very proud of her son at this point, and thought he had finally grown. Therefore, Nana thought there was no need for her to stay and miss today's early sale at the market. She did not forget she'll have to cook twice as much the moment Tsuna return home from school later. Her husband's salary had just arrived after all. There was no need to hold back from celebrating her Tsu-kun's first day.

On the other hand, Tsuna simply watched his mother leave. A lot of the parents around were looking at him with admiration. Their own sons and daughters were still hugging their skirts or pants, crying and not letting go, but this brunette... what a smart and obedient kid he was, they thought. Very dependable. Such words were said behind Tsuna's back. But the brunette himself was too preoccupied to even mind their praises (all the more earning him praise for being "humble" and "innocent").

Meanwhile, in his own little mental world, Sawada Tsunayoshi was undoubtedly concerned. Forget his friends and family worrying after finding him gone, he couldn't even return himself! He had tried every silly thing he could think of to reverse everything that happened, but failed. In the end, he almost died, was almost late to school and almost disappointed his mother. Even though he was still unfamiliar of this world's Nana, he still didn't want to see his mother sad and disappointed. (Or more like... he's just a competitive chuuni brat that wanted to act mature and independent. Nothing wrong with it, though.)

Tsuna sighed.

On the upside, however, even with the failed attempts, he still did gather plenty of information on his way to school. One being that: This world... ran parallel to his own. It was different from being transported to the future by a bazooka.

First, the time and date when he was zapped by lightning coincided with this world's as well. His identity and age was similar to his past. He was named Sawada Tsunayoshi. His mothers also looked alike and were named Nana (except, he had to admit, his mother in his old world was a lot cooler, being a renowned shinobi and all that). He hadn't seen his father personally yet, but from the family pictures scattered about in the house, he also looked similar. What more, the name of the town was also the same, Namimori; however, instead of it being old fashioned with houses almost made of reinforced bamboo, everything around here was made of cement and concrete. Tsuna could definitely say this place was more... modern. Not that his old world wasn't.

In his original world, Namimori was controlled and protected by an old and powerful clan, _his_ family, the Vongola. As such, even with the technological advancements, Vongola had exquisite tastes and still adhered to classical styles and old traditions. Hence, cars were still vintage in design despite most of them installed with artificial intelligence, the streets were cobbled and there still existed horse-driven carriages. There was also more nature than there are buildings.

There was none of that in this version of Namimori. The people looked very familiar, but at the same time not. And when he asked his mother if she knew of Vongola, she was honestly confused before answering no.

"Ahahahaha! Nice meeting you too! I hope we can be friends!"

An all-too familiar voice snapped Tsuna from his trance, before his sights led him to a boy sitting next to him. Said boy was slightly taller for his age, sported a short, spiky black hair, and had a smile as he looked at the kid on his other side.

The brunette was nearly lost in his new set of thoughts. Of course, he also knew who this boy was... or at least supposed to be. It was just that he didn't expect to meet him this soon.

"Take...shi." It was only above a whisper, but the lad — Takeshi — still heard it nonetheless. He turned to the brunette with mild surprise, still with that all-too familiar smile. "Hello! So... what's your name? I'm Yamamoto Takeshi!"

"!"

Tsuna didn't expect his soft call could still be heard by this world's Takeshi. After all, based on his observations, even if the people of this world looked similar, and even had the same identity, their backgrounds, skills and even their personality were largely different. Take for example that friendly granpda next door, he was once a gloomy one that lived in the forest by their mansion, and that gentle obaa-san who sells freshly baked bread! In the old world, she was a cranky seller of high-grade weapons on a far-off town. Even his once cool maman was reduced to a naïveté one, no offence really.

That said, obviously, Tsuna had known of a Yamamoto Takeshi in the past. Had grown with one, in fact, along with another boy named Gokudera Hayato. Their parents were friends, so it was natural that they would be too. The three of them were considered best friends, inseparable, and always competed for being the best in class. It wasn't a formal class, but still a class nonetheless, where the young shinobi went.

 _That_ Yamamoto Takeshi had monstrous senses. It was one of the things he secretly admired from his friend. In the past, despite his very young age, Yamamoto Takeshi was a natural in terms of both stealth and spying, an all-around combat genius and expert in the swords. But he wouldn't count on that in _this_ world's Takeshi. Thus, it really caught him off-guard for this stranger-swordnut to not just have the exact same smile, but also display a glimpse of his acute senses... Maybe this world wasn't as largely different as Tsuna thought it would be?

"Uhh... hello?"

It took a moment before Tsuna could register his classmate, this world's Yamamoto Takeshi, was talking to him. "Umm... Tsuna. Sawada Tsunayoshi. Please call me Tsuna!"

"Hahaha, nice meeting you Tsuna! Ah, right, you can keep calling me Takeshi!"

"En, nice meeting you, Takeshi," Tsuna's voice gradually softened at the end. This lad was Takeshi, but not him at the same time. This was all so confusing! But the young Tsunayoshi had no choice but to accept.

.

The rest of the day went on without a hitch... except Tsuna had undoubtedly made a name for himself. Because he had shown dexterity and fast reflexes on a getting-to-know game they played in homeroom, his classmates began considering him their future sports god in class. Couple that with his gentle face, his innocent smile, but quiet and mysterious image, he was instantly regarded as their "cool" classmate. Takeshi had laughed at him for that, and even called him awesome.

The two of them became close friends, or at least the closest you could get on a first meeting. They ate lunch together, and even teamed up on group tag in the afternoon. They even went home together, with their homes coincidentally near each other. Takeshi had invited Tsuna at their place, and Tsuna did the same, especially after coincidentally meeting his mother near Sushi-ya. In the end, the full-blown feast Nana had prepared were all consumed and Tsuna had re-met Takeshi's father, Tsuyoshi, and even ate some at their sushi restaurant. In his old world, the Yamamoto's didn't have a sushi place, but they do own a dojo...

"You okay Tsuna?"

Tsuna looked at his newfound (relatively, newly re-found) friend and smiled. "En."

So far, everything was good, and Tsuna meant that. He was happy. Because he met Yamamoto Takeshi. And whether in the old world or in this new one, he seriously wanted to be friends with one Yamamoto Takeshi. If he couldn't go back, might as well make do for what he can for now. All that's left was to hunt down the others.

* * *

 _Meanwhile, in another alternate universe..._

One minute, one young Sawada Tsunayoshi was woken up by his loud alarm. The next? When he thought he was just falling off his bed, he had fallen off a cliff instead! And felt burning sensation all over his body.

"IteeeEEEeeEEeE"

Birds flew from all direction upon his loud yell. But he wasn't to blame! He was seriously aching all over! It was even surprising he wasn't dead yet. And what was this? Where was he? The moment he came about, all he saw were trees! What happened to bed? How did he get here? Not to mention, his arms were tinged black. So maybe he was indeed burnt? Why? How? So many questions, he was so confused. Utterly lost.

Tsuna clenched his fists and tried to get up. No matter the situation, though, he had to flee this place. He was in the middle of the goddamned forest! It was a good thing it was still morning. Otherwise... the young brunette shuddered at the thought. His senses screamed danger all over! He really have to leave. Now.

Hence, despite his body's protests, the young Sawada Tsunayoshi who at the same time was also _not_ Sawada Tsunayoshi willed himself up. He grabbed a nearby stick to support himself. However, before he could take another step... _duck,_ his senses screamed and so he did. Unfortunately, his body still hurts that he easily lost his balance and uncharacteristically fell on unforgiving ground.

As he came about the second time, a man had stood not too far from him.

"Ciaossu."

.

In the years to come, the same young Sawada Tsunayoshi would think back to this time and realise his first death was not when he was transported in this world, _no_. Rather, it was during that time he had met this madman from hell. And he would wish he had died right there and then. But, of course, it was too late for all that. Because it will happen in the distant future after all, and it was too late... for he had already successfully taken the mantle of the Vongola Shinobi clan.

* * *

I had this idea for a one shot, but the moment I wrote it, multiple subplots came into mind. I might get back on this after finishing (or maybe when I am near halfway) my other story so it's one shot for now. I really write slow, so I don't think doing two at the same time is a good idea, but I will try my best!

Please tell me what you think and leave a review on your way out. Please don't forget to support my other story, The Parallel Rainbow too! Thank you very much! :D


	2. Chapter 2

Sorry for being so fickle! I thought I'd be updating TPR today, but had this one done up earlier instead (even though I said I'll look at TPR first)! I'm having troubles with a chapter on that one, but since this was giving me more ideas/inspiration lately, I just let it take its course and this happened. lol

Thank you very much for all those who added and reviewed!

Also, addressing **AkabaneKazama's** question: _"Will u write the normal Tsuna daily life too?"_ If by normal, you mean the non-ninja Tsuna then yes, but not all the time. Based on my initial plans, it's not really part of the central story. Kind of like a few scenes here and there at the end of some chapters for thrills. So its timeline might be different from the main story. lol

* * *

 **Title:** Body Switch

When Tsuna was eight, he met his father. _This_ world's father.

At that time, he only had one impression: _Average_. He wasn't exceptional like his old man in the past... but then again, he also can't say for certain. After all, Sawada Iemitsu _still_ do work for the Vongola. Yes, _that_ very same Vongola. Tsuna found out. As to what kind of work it was, Tsuna still wasn't sure. But if he was to guess, perhaps their leader. After all, his father _was_ the leader in Vongola clan back in his world, thus the reason for making Tsuna the heir in the near future. Thus, the brunette kid can't completely rule out the possibility. Hence, despite appearing idiotic, this papa of his might still have some hidden skills of his own.

"Tsuna!" Just when Tsuna was still lost in his own thoughts, his father tackled him in a hug before lifting him up. "Hahaha! Look how you've grown, Tsuna! Papa haven't seen you since you were five. Did you miss papa?"

Tsuna tried his damnest not to flail and wail like a kid, but this was too embarrassing! He was _not_ used to this kind of Iemitsu. He glared at his father. "No," and flatly replied. Tsuna missed his _own_ father, yes. But this version of Iemitsu was still a stranger to him, so how could he miss _this_ father?

If Iemitsu felt hurt by what his son said, he did not show. Instead, he only tightened his hug on Tsuna. "Then, I'll make sure you'll miss me the next time. Hahaha!"

Iemitsu only let go when Nana called them for lunch, much to Tsuna's chagrin.

And ever since then, he would try his best to avoid his old man at all cost.

Perhaps he had spoken too soon.

=.=.=

And spoken too soon, he really did.

"You okay, Tsuna?" both Yamamoto Takeshi and Sawada Tsunayoshi were walking together to Namimori Elementary. Although the brunette was silent most of the time, it was the first time the raven-haired boy saw him so dispirited. He never fully understood the brunette, true, even after being friends with him for nearly a year. Still, Yamamoto Takeshi did not mind. Instead, seeing Tsuna disturbed still made him feel a bit concerned.

Tsuna grunted in reply.

There was a lot on his mind right now. For one, after working overnights cracking codes here and there, he finally and completely sniffed Vongola's main base in Italy, only to find out they were part of the mafia. Mafia! Not ninja! What the hell do mafias even do?! What more, his dad wasn't the leader, but some external advisor. Instead, his uncle was the one considered the Nono. How was he to stomach this? He is _not_ the heir! Is he even blood-related to this world's Vongola? What was he to do with all his trainings?

Tsuna had thought of researching more of it early this morning, but secondly, his father was being too nosy. Going to his room so early in the morning to invite him out for fishing! After finding out the full truth, he was still bitterly disappointed with his father. And it only made him dislike him more for not leaving him to research in peace. It was giving him a headache. And he still had that problem of hunting down the rest of his friends! One year passed and no trace of them yet... none other than Yamamoto Takeshi.

Not to mention a fourth problem of finding ways to return home.

"Hahaha! Just cheer up, Tsuna!" the taller kid slung an arm around his friend. "It's bound to turn out great later on!"

The brunette was skeptical on those words. He had been to numerous assassination attempts and near-death situations ever since he was a baby, and he learned the hard way that things will _not_ "turn for the better" lest he do things himself and work hard. If he want good results, he has to work.

Tsuna tried organising his thoughts. Looking at Takeshi's happy smile, it honestly made him feel a bit jealous. The Takeshi of his world was also the same, a happy fellow, except that version of Takeshi knew his circumstances and even offered to share the burden off of him. What was he suppose to expect on this version of Takeshi? He can't possibly just tell him 'Hey, I came from another world, is an heir-apparent to some ninja clan so I got skillz. But now, I don't know how to go back or even what to do with all these things.'

Sometimes, he blamed his upbringing for maturing early. Training and planning was drilled on him since young. Being an heir to a powerful ninja clan was hard.

Tsuna sighed.

=.=.=

Today was the start of a new school term in Namimori.

So even if it was nearly 8 in the morning, both Tsuna and Yamamoto had encountered a lot of their schoolmates still heading to school. Being used to vacation, no doubt a lot had almost slept in on the first day of class. By the time the two were near the school gates, a lot of the students had gathered by the entrance up ahead.

"Is there some event happening today?"

Tsuna shrugged. Maybe a lot more students were late than they expected-? Before they could ask a nearby senpai, however, _WHIP! BAM!_ Fighting broke out at the exact same place the crowd had gathered. Did the teachers suddenly became too brutal on latecomers?

Tsuna and Takeshi looked at each other, before breaking into a jog.

Upon closer inspection, however, the sight that greeted them wasn't a teacher disciplining the students... but another lad with raven hair and slanted eyes, tonfas on both hands.

"... _Kyoya?!_ "

Indeed, maybe things will turn out for the better soon... or not.

* * *

Meanwhile, in another world far, far away...

"ITtteeEeeeEee! Let go, let go, let go, let go!"

A lad by the name of Sawada Tsunayoshi was flailing and wailing like a kid. He was tackled on the ground with a death grip, by a man who suspiciously looked like his old man. "I give, I give, let go," he surrendered. The man got up before pulling his own son up.

"You've gotten weak, Tsuna! You used to give papa a hard time. Hahaha!"

"Che! Old man, that guy isn't even Tsuna," another boy of about Tsuna's age spat somewhere far. He was the lad who first noticed something was wrong on this Tsuna, the first to recognise he was no longer the friend they all knew. And since then, the lad had been antagonistic towards the brunette.

Tsuna rubbed his sore muscles, attempting to ignore the glares of a certain silverette.

Today was another weekly training with his "papa." Tsuna had been in this world for almost half a year, but not once had he scored a victory against the older Sawada, _yet_. It always ended up with him on the ground, battered and bruised. Seriously, what kind of life did the other him lead in this world?! _So scary..._

The man, Iemitsu, sighed. "Well, you may not be our Tsuna, but you are still my son... err, in another dimension, maybe. Hahaha!" he scratched his head. "You still have every right to be here, Tsuna. And to protect yourself, you have to grow stronger," he patted the lad in the head, slightly apologetic but still overflowing with care for the lad.

Even though it had been months, it still surprised Tsuna knowing his "father" was capable of such love. For all he remembered, he was negligent and annoying. This world's Tsuna was lucky.

The first time Iemitsu acknowledged this Tsuna was not his own, rather than sending him out or antagonising him, the first thing he did was relay instructions after instructions on how to better protect the boy. He had the face of a Sawada Tsunayoshi, but _not_ the talent of one. Without protection, and as a newbie, it will surely get him killed sooner or later.

There were times he appeared distant, yes, but not to a point it made Tsuna feel left out. He was also slowly teaching him from time to time about the people under the clan, and the things they do, so as not to make him look _too_ different. To this day, other than their closest relations, not one had realised the Tsuna they once knew had been _switched_.

"En, I'll... I'll do my best," was the only thing the brunette could say. Realising his weaknesses, he was a bit embarrassed. A spark of resolve lit within him.

"Hayato, please protect Tsuna. Reborn," Iemitsu looked at another man and nodded. Then, the two left the training area.

...

"Sugoi, Tsuna! You finally lit your flames a while ago! Hahaha!" a lad, Takeshi he was called, slung an arm around the brunette. Tsuna's brows knitted. His body was still aching and tired, but he tried not to complain.

"I did not expect you to be brutal, sword freak," the silverette, Gokudera, smirked. "The _real_ Tsuna-sama had already lit his flames a long time ago, aren't you just insulting this imitation-"

"Gokudera."

"..."

"Che! Suit yourself, but I will _never_ accept this imitation," Gokudera Hayato glared.

"Where are you going, Gokudera? Didn't Iemitsu tell you to stay put?"

The silverette didn't reply, before he too finally left the field.

"..."

"Err... you don't have to worry about me, Yamamoto-kun! But... umm, thank you!" Sawada Tsunayoshi smiled.

"Tsuna..." Yamamoto Takeshi sighed. "Just so you know, I wasn't insulting you, you know..."

"... I know."

Yamamoto Takeshi smiled. He wanted to say something more, but stopped in the end.

The young swordsman really missed competing with his best friend. In the past, it used to be Tsuna who would teach him things, Tsuna who topped the two of them. And one of the few people who could give Sawada Iemitsu a hard time in battle, the so-called once-in-a-lifetime prodigy in the ninja clan world.

But now, this brunette could barely fight, and barely remembered the things being taught to him. To that, it was a bit weird and awkward. He was already so used to having a friend who could handle himself too well, but now... Takeshi only found himself becoming apologetic more often realising they had him left out on combat or homework. He forgot he was no longer their old Tsuna.

True, the three of them have never been the same ever since their Tsuna disappeared and this brunette came instead. Still, one Yamamoto Takeshi truly believed it will be better soon. While Takeshi understood Gokudera's sentiments, unlike the silverette, he was not one to completely ignore and antagonise this new brunette. And if one only looked closely, this Tsuna had the semblance of the very same Tsuna he once knew. He was kind, accepting and never once complained. Not to mention... he had the instincts of a true shinobi.

His reactions, his intuitions... and that raging flame a while ago were proof.

This was also the reason why Yamamoto Takeshi started admiring the new Sawada Tsunayoshi. Yes, their old Tsuna had already lit his flames a long time ago. But this was the first time Yamamoto Takeshi had seen such pure resolve in his "best friend's" flames, purer and brighter than before. And so, like in the past, the young swordsman was still more than willing to help this version of Sawada Tsunayoshi.

Takeshi was hopeful Gokudera would realise it soon too...

"Hahaha! Let's go, Tsuna, before Reborn grills us. You still haven't finished the homework from yesterday!"

The brunette complained a million times in his head. But he was too tired to even say a thing. He only sighed, before letting Yamamoto Takeshi drag him to who knows where.

* * *

Thank you very much for reading! Yay, please tell me your thoughts! :D Thank you!


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